Ayoub S F
Acta Anat (Basel). 1979;105(1):25-36. doi: 10.1159/000145103.
The anatomy of the external anal sphincter was studied in 20 adult human cadavers of both sexes by dissection and histological examination. The external anal sphincter is not naturally divided into layers or laminae. The lowermost muscle bundles differ from the main part in being completely surrounded by thick fibrous tissue septa derived form the longitudinal anal coat. The perineal branch of S4 supplies the posterior third, the inferior haemorrhoidal nerves supply the anterior two thirds. All fibres of the sphincter retain their skeletal attachment to the anococcygeal ligament to the coccyx. Some fibres cross the median plane to be continuous with the transversus perinei of the opposite side. A cleft was displayed separating the lower border of the levator ani muscle from the upper border of the external anal sphincter. The muscle bundles of the sphincter are arranged circumferentially in one continuous circle and not in loops. Fibres from the anterior border of the levator ani muscle extend to cover and blend with the outer surface of the external sphincter in their way to the anococcygeal ligament.
通过解剖和组织学检查，对20具成年男女尸体的肛门外括约肌进行了解剖学研究。肛门外括约肌并非自然分层。最下部的肌束与主要部分不同，其完全被源自肛门纵肌层的厚纤维组织间隔所包围。骶4的会阴支供应后三分之一，痔下神经供应前三分之二。括约肌的所有纤维均保持与尾骨的肛门尾骨韧带的骨骼附着。一些纤维穿过正中平面，与对侧的会阴横肌相连。显示出一条裂隙，将肛提肌的下缘与肛门外括约肌上缘分开。括约肌肌束呈圆周状排列成一个连续的圆圈而非环状。肛提肌前缘的纤维延伸并覆盖肛门外括约肌外表面，在其延伸至肛门尾骨韧带的途中与之融合。
